JPH03500903A - coal additives - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Name of invention) Coal additive The present invention relates to the combustion of sulfur-containing fuels, and more particularly to the combustion of sulfur- and sodium-containing fuels. Capturing and retaining other undesirable compounds in solid form during fuel combustion related.

If sulfur is captured and retained, preferably in solid form, during combustion, the air produced by combustion Reduce the amount of pollution. Normally, sodium evaporates during combustion or becomes a gas. Sodium traps to cause slop and blockage on boiler heat transfer surfaces after It is desirable to maintain the same. High sodium content with many attractive aspects Coal is not used for this reason and is low cost.

June 18, 1985 for disclosing a process for burning sulfur-containing fuels. U.S. Patent No. 4,523,532 (Moriartoli et al.) issued in 1985 U.S. Patent No. 4,517,165, issued May 14, ). The contents of these two patents will be described here as reference.

The processes disclosed in these patents are called low NOx/SOx burners. It has been extensively tested with two known experimental combustors. At first coal fuel combusted and similarly combusted with high sulfur residual oil. During these processes, combustion The material is first combusted in a first stage, producing a solid sulfur bond-retaining compound that can be heated using conventional heat. The sulfur is captured in solid form with a binder at a temperature that keeps it in a reduced state as predicted by mechanics. Ru. Furthermore, at a later stage, in a somewhat lower reducing state and below the fusion temperature of the binder. burns fuel at a higher temperature. The combustion state in this later stage is similar to that of conventional thermal power. According to science, the captured sulfur is lost (i.e., oxidized to gaseous sulfur form). do). Capturing fuel sulfur in solid form during combustion using a solid binder is This is a well-known technique. For example, US Patent No. 26, 1985, , 4,555,392 (Steinberg) is used in Portland as a sulfur scavenger. Discloses the use of cement. Similarly, the fuel for ideal sulfur capture is Firing conditions and binders are disclosed in the Moriarty et al. and Moriarty patents and are herein incorporated by reference. Described. However, holding the sulfur in solid form as a subsequent step is This technology was not commonly practiced in the past.

A combustion process that captures and retains sulfur and other undesirable compounds in solid form during combustion. It is hoped that the emergence of

Accordingly, in one aspect, the present invention provides a process for combusting sulfur-containing fuels.

A mixture of fuel, sulfur binder and sulfur retention material is placed in a first combustion zone. this mixture , temperature and multi-fuel chemistry that captures virtually all of the sulfur in solid form with a sulfur binder. Burn in the first zone according to stoichiometry. The sulfur is chemically bonded to the binder and further Second, the scavenged sulfur compounds are physically and chemically incorporated into the retaining material. this Due to multi-fuel gases and solids, combustion products including sulfur production fly ash and slag occurs.

Furthermore, these combustion products are subjected to at least one additional treatment at a temperature above the melting temperature of the solid. Burn in the next multi-fuel combustion zone to melt the fixation. This next combustion zone Conditions typically thermodynamically promote the oxidation of trapped sulfur to gaseous form . Instead, in the present invention, the presence of the mixture allows the trapped sulfur to bind to the retained material. further interact in the fused state to form a stable fire-resistant composite compound. Ru. The sulfur is thus encased in the molten refractory mixture, thereby causing high temperatures It is also protected from oxidation and gasification in the subsequent zone of oxidative combustion. Natoriu Other undesirable combustion components, such as smoke, can be advantageously captured by the above process as well. can be captured and retained.

Reaction of the sulfur with the binder enables sulfur capture. Captured sulfur and retention material Improved retention of trapped sulfur in subsequent interactions, resulting in less vaporization. improved comprehensive control of sulfur effluents. The hardness that occurs there Some of the body products are refractory and therefore can withstand even higher temperatures and oxidizing conditions. Resistant to reactions. The sulfur captured and retained in this way is It is not oxidized and does not turn into gaseous sulfur dioxide even under the highest oxidation conditions. .

Preferably, the sulfur binding material is calcium-based and the sulfur-retaining material is silicon-based. It is to be. The molar ratio of calcium to sulfur in the fuel when used is low. The molar ratio of silicon to calcium used for scavenging sulfur is preferably 0.5. 6 to 1.2, preferably 0.8 to 1.0.

Although applicants do not wish to be bound by any particular theory, these molar ratios are advantageous. This can be trusted by the following explanation. Calcium converts into sulfur and salt at high temperatures. Calcium is used to scavenge sulfur to form a stable compound. difference Additionally, calcium can also be refractory composites with other common materials such as silicon and aluminum. form a compound. Calcium must be present in sufficient quantities to scavenge sulfur. However, the mere presence of calcium is no guarantee that sulfur will be captured. stomach. First of all, the fuel must have the right air-to-fuel ratio and temperature conditions to trap the sulfur. It won't work unless it is burned. Calcium is utilized at the same time as it is burned under appropriate conditions. The combination of these two factors traps sulfur.

In conventional computer calculations of combustion thermodynamic equilibrium, carbons such as anorthite and pseudowollastonite are Even the common refractory compounds of lucium, silicon, and aluminum cannot be typically described in structure. I can't. Although many of these compounds are well known, the necessary thermodynamic data are not available or have not yet been incorporated into equilibrium calculations. Sara In addition, sulfur has many chemical effects, including displacing lime and forming calcium sulfide. It is well known that compounds and oxygen can easily be substituted. Oxygen and sulfur are on the periodic table They are neighbors on the same level and are therefore chemically similar. Therefore, it has not yet become concrete. , under sufficiently high temperature and fuel-rich combustion conditions, sulfur is absorbed by these composite refractory calcium, It can replace oxygen in some silicon and aluminum compounds.

Such sulfur-substituted refractory compounds do not normally occur. As a result, this Thermodynamic data on compounds are not available and are rarely included in equilibrium combustion calculations. Not yet. In the absence of complete thermodynamic data, higher It is necessary to assume unbalanced retention of trapped sulfur in high-temperature combustion and further in the oxidation region. There is a point. However, the resulting sulfur-containing compounds are less stable than the starting materials. It is predicted that the material will exhibit fire-resistant properties.

Under high temperature, highly fuel-rich combustion conditions, the thermodynamically preferred form of sulfur is solid. Calcium sulfide (CaS) is generally found in current thermodynamic equilibrium calculations. is shown. For this, a molar ratio of calcium to sulfur of at least 1:1 can be used. , indicating that all of the sulfur is trapped in this solid form. However, the stone Considering the considerable data taken into account from the analysis of charcoal combustion and coal ash (ignition basis) , sulfur is actually captured at a ratio of 1 mole of sulfur to 2 moles of calcium. It shows. Similarly, sulfur is similar to magnesium, sodium, and potassium. Captured by other basic elements.

In the absence of retention material, the sulfur trapped by calcium is generally lost in later combustion stages. Not retained. Sulfur captured by magnesium generally remains Not retained in later combustion stages.

Solid calcium sulfur compounds must interact with the retention material to ensure retention of trapped sulfur. action and/or reaction may be required. The preferred retaining material is silicon, and in some cases Contains some aluminum. To ideally retain trapped sulfur, The molar ratio of silicon to calcium involved in scavenging sulfur is at least 0.8. . For example, if the calcium/sulfur molar ratio is greater than 2, then 2 moles of calcium Only 1.6 is involved in the trapped sulfur, so a silicon/sulfur molar ratio of only 1.6 is required.

Aluminum appears to have limited sulfur capture, at least from the available data. I found out that it doesn't seem like it. Most of the research data is based on aluminum calcium The molar ratio of umium to silicon is less than 1/3. aluminum is diuretic sulfur retention was actually 1/3 of that measured with these fuels.

The well-known refractorification carried out without alumina with a calcium-silicon molar ratio of 1:1 The compound is pseudo-wollastonite (Cab, 5i02). Analyzes of such compounds For lobes, it contains both calcium and silicon in a 2:1 molar ratio to sulfur. This means that 2 moles of pseudo wollastonite are two molecules of limestone (CaO, CaS, 2S +02　) indicates that it is involved in replacing one of the oxygens with sulfur. doubt Wollastonite has a melting point of 1540°C (2800°F). The sulfur-containing analogue Special table 13-500903 (3) It is naturally expected that it would have fire-resistant properties.

Other compounds such as sodium can be used in the same way as sulfur compounds in the process of this invention. Therefore, it is thought that it can be captured and retained in solid form. For example, limited combustion balance meter In calculation, sodium can be expressed as Na2O, A1□05 and Na2O,2Si02. Indicates that it is held in the form of a compound.

Again, in these equilibrium calculations, the very fuel-rich combustion conditions that cannot be captured in this way If the sodium is not restrained in complex chemical forms such as these, it will In a subsequent step it is oxidized in higher oxygen and higher temperature conditions, vaporized and encased in a molten solid. Indicates that the

The invention relies on the use of solid and liquid fuels. Necessary sulfur binder and The supporting material may be inherent in the fuel or may be added. Preferably sulfur The binding material is calcium-based, and the sulfur-retaining material is silicon-based. It is better. Lower-rank lignite and subliminal coals often contain sufficient amounts of both materials. I'm here. High-ranking bituminous and anthracite coals usually contain very little calcium. , silicon is insufficient for sulfur and both must be added. liquid fuel The material, of course, does not contain any of these solids.

The desired overall calcium to sulfur molar ratio is 1.5 or greater; The most suitable is between 1.5 and 2.5. The molar ratio of silicon to calcium is Advantageously it is between 0.6 and 1.2, preferably between 0.8 and 1.0. calciu If aluminum and silicon must be added, these materials can be used in almost any form. may be added, preferably in low cost forms such as limestone and sand.

Depending on the type of coal, sulfur can be replaced by other basic substances, primarily magnesium. Priority capture. The resulting magnesium-sulfur compounds are removed by the retaining material. will not form a suitable composite. The sulfur captured by magnesium is Large amounts are lost in later combustion stages.

Moreover, the preferential scavenging of sulfur by these materials reduces the desirability of sulfur by calcium. Preventing proper capture. Many Sabiraminus coals and brown coals contain half the amount of calcium. Contains gnesium. In these cases, 1/3 of the amount of sulfur contained in the fuel is preferentially The remaining 2/2 is captured by magnesium and available for capture by calcium. It's 3. Excess calcium does not compensate for magnesium. It seems that there is no such thing. Therefore, in such cases, the desirable calcium in coal The amount of sulfur remaining available for scavenging by calcium, i.e. 2:1 for the amount of sulfur not previously captured by other basic substances such as sium. Any amount sufficient to provide the molar ratio may be sufficient. In other words, the molar ratio of the basic components is , at least metal ions, magnesium, calcium, sodium, potassium including 2:1 to sulfur.

Ideal sulfur capture and retention combustion conditions are described in the patents of Moriarty et al. The existence of a sulfur binding material and a sulfur retaining material as disclosed in the patent of This allows the melting temperature of the solid to be advantageously lowered. Therefore, the first aspect of the present invention The two-zone combustion temperature is below the lower end of the temperature range reported in these patents, i.e. That is, as long as it is higher than the melting temperature of the solid, it may be as low as 1600°.

Typically, at least one other combustion zone will combine with the two zones included in the invention. It is used as This last zone ensures complete combustion of the fuel in excess air. It takes. The present invention allows the sulfur-containing solids to complete the final combustion zone without losing the trapped sulfur. It is possible to pass through the area. Otherwise, solids should be removed before they enter this zone. Bye.

The invention will also be described in more detail with reference to the following examples and accompanying drawings.

Hereinafter, embodiments will be described with reference to the drawings.

Figure 1 shows the measured amount of sulfur retained in coal ash and the calcium versus sulfur content in burned coal. 1 is a diagram of ASTM ashing data showing correspondence between yellow mole ratios.

Figure 2 shows the CaO/CaO of Sabiraminus coal burned in a burner with low NOx/SOx. It is a ternary diagram of AIz03/Si%.

The third figure shows bituminous coal as it was mined and bituminous coal burned in a burner with low NOx/SOx. It is a ternary diagram of CaO/Al2O3/5in2 of blue coal.

Husband n Takumi Standard ASTM analysis of coal ash on an ignition basis involves It also includes burning coal. 24 analyzes of coal ash extracted from coal mines sample was extracted from the coal data book. Five additional ASTM ash analyzes Obtained from a mixture of coals tested in a low Ox/SOx burner. This N Performance data from burners with low Ox/SOx will be considered in Example 3.4.5. Ru.

Combustion in a manfur furnace is relatively low temperature, but sulfur is trapped and retained in the ash. It is reported as SO3. Under these conditions, sulfur interacts with calcium. It is captured by both Gnesium and Gnesium.

The temperature is low enough to retain all trapped sulfur.

A sample of data from the Coal Data Book includes six Montas, North Dakota brown coal, four Colorado, Montana, and Wyoming Sabiraminas coals, ten different Contains 14 bituminous coal ash plates from the states of After all, a burner with low NOx/SOx One of the five coal blends tested included Wyoming Sabillaminus coal. , the remainder includes bituminous coal from Indiana, Pennsylvania, and Nova Scotia. limestone and sand, various combinations of calcium and silicon, and in some cases powdered aluminum. was added to the test coal. How many low-ranking coals are in the sample of data? The amount of magnesium was more than half the amount of calcium. high ranking stone The amount of silicon in some of the charcoals was lower than half of the amount of calcium. this sample All data are from ASTM ash analysis of these coals and coal/additive mixtures. This is not an analysis of the ash produced by the combustion of a burner with a low NOx level of 150χ.

Molar ratios of silicon to calcium for all but two of the coal ash data samples. was greater than 0.8. Two exceptions are shown in Figure 1. Figure 1 shows the contrast of silicon. Coal with a lucium molar ratio greater than 0.8 has a calcium to sulfur mole ratio. Figure 1 shows sulfur capture and retention in ASTM coal ash in good agreement with a 2:1 ratio. day The limit of the and The experimental correlation of that data is 14.6% with a correlation coefficient of 0.92. It shows an average molar ratio of 1.93 with a standard error of estimation of . This is a fairly good correlation. 2:1 molar ratio is within the uncertainty of the correlation. Examine the data in detail The measured sulfur uptake is from a 2:1 calcium/sulfur molar ratio (lignite). At higher than expected levels, the amount scavenged by magnesium is generally It turns out that the price is high.

On average, the silicon content in the correlated lignite and Sabiraminus coal data shown in Figure 1 is The molar ratio of calcium to calcium is 1.38, which is that of as-mined bituminous coal. It was higher than The three brown coals have an average silicon to calcium molar ratio of 0.89. This is a low level. Among the four bituminous coals tested using ASTM analysis Calcium (only) was added to the first two types of coal, and calcium and silicon (only) were added to the first two types of coal. Alumina) was added to the second two types of coal. As a result, silicon versus cal The average sium ratio was only 0.42 for the first two, but 0.42 for the second two. It was 87. The first indicated as “(Sl/CA)<0.5” in Figure 1 The retention of sulfur in the coal ash of the two types of coal is greater than that of the other coal due to one or more factors of both types. The sulfur retention in the ash of They were the same, but the ratio of silicon to calcium was higher. On the other hand, calcium When sulfur and silicon were added to these bituminous coals, the retention of sulfur Comparable sulfur retention. In the case of these four types of bituminous coal, the low temperature state of the Matsufuru furnace However, it is not enough to provide enough calcium to scavenge sulfur. It shows that That is, there must be adequate silicon to retain the trapped sulfur. Must be.

Ki Takumi NOx similar to the burner disclosed in the above patent of Moriarty et al. Low SOx burner, using California high sulfur residual oil as fuel. A series of three tests were conducted. This oil contained 4.51% sulfur. 1 In one test, sufficient amounts of stone were used to provide a calcium-sulfur molar ratio of 1.88. Calcium in the form of ash was added to the oil. This is a 2:1 calcium-sulfur model. This ratio is sufficient to capture 94% of the sulfur in the oil. In these tests Only the first and second stages of the burner were operated.

Sulfur uptake was measured at both stages. In the best sulfur scavenging conditions, an average of 89 sulfur % captured. But without silicon or any kind of retainer in the mixture Then, all of this trapped sulfur will be oxidized and become SO□ before reaching the chimney. expected. This burner has no chimney, but 24% of the captured sulfur is lost in the second stage. By the end of the second stage, only 65% of the sulfur can be controlled.

It is expected that even larger amounts of trapped sulfur will be lost during later combustion stages.

The conclusion here is that in addition to calcium, other This means that a substance is necessary. A mixture of approximately equal masses of calcium and silicon When added to the oil, a desired molar ratio of about 2:1 to each sulfur It was predicted that the retention of trapped sulfur would be significantly improved.

Support 591 The Matsufuru furnace and low NOx/SOx burner used for ASTM ash analysis were , the final oxidation stage of the burner with lower NOx/SOx than occurs in the Matsufuru furnace. also exhibits a somewhat similar combustion process, except at higher temperatures. Flyanche composition and the extent of sulfur capture is the same as on the ASTM ash analysis ash side of the coal in the early stages of the burner. This is expected to be the case. However, later on, in the burner, the captured Sulfur that is not retained reliably, even if removed, is oxidized to gaseous sulfurs.

Fly ash extracted from the baghouse of a burner with low NOx/SOx The measured sulfur concentration and the ASTM ash analysis of these same coals The difference in sulfur is indicative of sulfur that is initially captured but not reliably retained.

A total of 7 coals and coal/additive mixtures in low NOx/SOx burners It was burned with. A full minute of baghouse fly ash from five of these The analysis results were obtained. Table 1 shows that bugs in coal ash and fly ash in these tests Showing the sulfur held in the house. These differences are in the ASTM Matsufuru furnace. The amount of trapped sulfur during high-temperature combustion in burners with low NOX/SOX is proportional to low-temperature combustion. Indicates a loss. In the final column of Table 1, the molar ratio of magnesium to sulfur is 1/2. Indicated by This stage shows the coal ash at a magnesium to sulfur molar ratio of 2:1. effectively indicates the percentage of sulfur captured by magnesium in

Table 1 Sulfur capture percentage % Test No., coal ash fly ash loss, ash-Mg/2S baghouse mole % 31 99.4 56.3 43.1 26.832 40.7 55.1 - 14.4 2.833 25.7 38.4 -12.7 2.834 62. 6 64.7 -2.1 2.735 55.7 57.3 -1.6 2.7 The coal burned in Test 31 had a calcium and magnesium to sulfur molar ratio of 2. 31 and 0.54 hippo low sulfur Western Svitminous coal. Exam 3 The coals burned from 2 to 35 are actually high-grade coal with no magnesium content. It was a sulfurous Eastern bituminous coal. The data in Table 1 is based on the ASTM standard for bituminous coal. Most of the sulfur captured and retained during the ash formation process is caused by low NOx/SOx This indicates that it was lost on its way to Burna's bughouse. However, bituminous coal Regarding sulfur capture and retention, the sulfur capture and retention in the burner is similar to that of the ASTM ash plate. It was almost the same. No apparent loss of trapped sulfur in the burner In addition, sulfur is also exposed by fly ash on the way to the baghouse. clearly captured. The key difference between Subituminus and bituminous coal is the magnesium content. It is a relative concentration. This means that magnesium is preferentially used in coal ash over calcium. Alternatively, sulfur is captured in fly ash, with or without a retention material. This indicates that the trapped sulfur is lost during the later combustion stages. magnesi in coal The presence of sulfur thus effectively controls the escape of vaporized sulfur. It could be a hindrance.

Eclipse ( A large amount of low sulfur Western Subituminus coal is used as the low NOx/SOX coal. Tested with burner. These coals have a combustion rate of oxides of calcium and silicon. , are shown in Table 2 together with the molar ratio of aluminum. All of these, with the exception of Kaibaroisotu, All coals were tested at 1 ton per hour in small scale low NOx/SOx burners. I tried it.

Kaibarowitz is a burner with low NOx/SOX at 15001b/hr. Tested. Oxides of calcium, silicon, and aluminum in coal ash during combustion The proportions are summarized in Table 2 and shown in Figure 2 as weight percentages of the total of these three components. Shown in ternary diagram. The table shows the ratio of calcium to sulfur and the ratio of silicon to calcium in coal. It represents the molar ratio and percentage of 1/2 of the sum. The highest possible capture and retention of sulfur is approximately 2:1 molar ratio of umium to sulfur and approximately 1:10 molar ratio of silicon to calcium. These molar ratio data provide the highest sulfur capture and retention assuming that I predicted it. All these coals were tested under the multi-fuel, high temperature combustion conditions mentioned above. Ta.

Low Sulfur Western Svitsuminous Coal (When Burned) (Data expressed as percentages) ) Test No. Stone charcoal CaO5in2A1203 Ca/2S Si/Ca (wt) (wt) (wt) (mol) (mol) XX Power Iparou Zitz 23 59 18 89 24123 White Wood 1.4'68 18 196 46224 Blank Mesa 1], 65 25 1.01 56130 Spring Creek 30 49 21 83 15431 Hippopotamus 34 4.8 19 117 12936 White Wood 41 45 14 830 103 All of these coals require a calcium/sulfur molar ratio of approximately 2=1. Assuming that the calcium/sulfur molar ratio is 83 percent of the sulfur or higher, Large enough to capture the top. In tests, approximately 70% or more of sulfur was not captured. The difference between the maximum allowable and the actual uptake is due to the dryness of magnesium in the coal. It is thought that there is interference.

These coals all have a low silicon/calcium molar ratio, retaining total trapped sulfur. is large enough. Regarding how much sulfur is scavenged by calcium bind, mix, and combine to form a refractory mixture that ensures the retention of trapped sulfur. There is enough SiO. In all tests of these coals, the first stage of combustion The sulfur captured by calcium at It goes through the combustion stage and is retained all the way to the baghouse.

Among the composite refractory compounds formed from these coal ash, Figure 2 shows white wood. The first combustion of the dead and blank mesa coals formed widespread anorthite, and the remainder was similarly suspicious. This indicates that quasi-wollastonite refractories are expected to form primarily.

The predicted molar ratio of calcium to silicon for pseudowollastonite (CaO5iO:L) is 1:1. However, directly substituting CaS for CaoO reduces calcium's sulfur motive power. It was shown that the ratio is 1=1. The most promising sulfur-containing refractory compounds are CaO, Contains 2 mol of pseudo wollastonite as CaS, 2Sj02. In any case, this The ash of all these coals contains several types of ash, including calcium-silicon and aluminum. in suitable proportions to form a composite refractory compound.

K skin application 1 NOx/SOX five mixtures of high sulfur Eastern bituminous coal and binding/retention additives Burned at low burner. These coals and the appropriate test data are available as they are mined. and coal during combustion are shown in Table 3. The table shows calcium, silicon, and aluminum. indicates the proportion of oxides in coal ash, and expresses the sum of the components of coal ash as a percentage by weight during combustion. . The proportions of calcium, silicon, and aluminum oxides are shown in a ternary diagram in FIG. difference Additionally, Table 3 shows a molar ratio of approximately 2:1 of calcium to sulfur and silicon to calcium. The prediction is based on the assumption that a 1=1 molar ratio is required for capture and retention, and the prediction and actual Data on sulfur capture and retention during production. Table 3 shows calcium as “capture”. The molar ratio of Mo to sulfur (Ca/2S) is shown in the table. 2:1 calcium /sulfur molar ratio is required, these Ca/2S ratios are Directly predict the percentage of sulfur in the coal that is captured in the first stage.

The molar ratio of silicon to calcium (Si/Ca) is shown as "retention." 1 A silicon/calcium molar ratio of 1:1 is required to retain all of the trapped sulfur. These Si/Ca ratios can directly predict the retention of scavenged sulfur, if desired. table The retention data shown in Figure 2 is based on the high temperature burner under normal operating conditions for each test. is trapped in the first stage and in the relatively more oxidizing second stage of the burner. Showing the highest percentage retention of sulfur. Theoretically, it is retained as a solid in the second stage. There is no sulfur present. Simulated boiler section of burner test equipment with low NOx/SOx Although there was less trapped sulfur loss further downstream, these operating conditions were It is not considered appropriate for the example. No retention data was obtained from Test 32.

Table 3 High sulfur eastern bituminous coal (Data expressed as percentage) Capture hold Test No. Coal CaO5iO1Al, 03 Ca/2S FIeas Si/ Ca Heas (wt) (wL) (wt) (mol) (a+ol) While mining coal 32 in 35' Seminole 3 72 25 1.6 -2644 -33' ゛Rank Building 6 62 32 3.4-944-34' Prince Mine 2 62 36 1.3 -2638 -38' Illinois #6 7 62 31 3.0-846 - During combustion 32 Seminole 59 27 14 121 70 43-33 Blank Building 60 27 13 76 71 42 5934 Prince Mine 41 4 1 19 77 68 93 7135 Seminole 42 37 21 67 63 81 8438 Illinois #6 37 51 12 90 68 12 895 Eastern bituminous coal typically tends to be acidic and naturally contains very little calcium. Most of it is silicon. Figure 3 shows the presence of excess water in the ash of coal as it was mined. There is surplus silicon and aluminum, and a complex compound of calcium, silicon and aluminum Tests 32 and 33 showed a large amount of calcium ( ) was added to the coal before the test. Figure 3 shows that the resulting mixture is the opposite of the ternary diagram. located on the side, resulting in excess calcium, and the formation of complex compounds of these substances is unlikely. Show that there is no need for it. However, in test 34.35.38, calcium and Add both silicon. The mixtures produced in these tests contained calcium, silicon and It was in the region of the ternary diagram that indicates the possibility of forming refractory compounds of aluminum.

Table 3 shows that there is little calcium in the as-mined coal. these Specific coal was not tested with a low NOx/SOx burner after being mined. However, all but a few percent of the sulfur is S, regardless of the method of coal combustion. It is well known that it is oxidized to oxygen. Therefore, it is captured in the burned coal. Most of the added sulfur is apparently due to calcium addition. This calcium is obtained from coal mining. It was simply added in bulk to raw coal before it was pulverized as limestone.

The actual amount of sulfur that can be captured in a low NOx/SOx burner is initially It depends on the combustion state of the first stage of the burner under test according to the combustion process.

However, according to the present invention, this scavenging occurs when the molar ratio of calcium to sulfur exceeds 2:1. I can't get it. Table 3 shows that in the test of coal used, from 67 to 100%. Based on a calcium/sulfur molar ratio of 1/2 to support sulfur capture in This indicates that sufficient calcium has been added. Measured sulfur capture from 63 The range was up to 71%. In three of these tests, the measured average sulfur Yellow capture was only 6% lower than expected. However, in exams 32 and 38 was 22 to 30% lower. The conclusion here is that in trials 32 and 38 Sulfur capture is limited by first stage combustion conditions, while from tests 33 to 35 Sulfur uptake in was mainly limited by calcium deficiency.

Table 3 shows that all of the sulfur is captured based on a 1:1 silicon/calcium molar ratio criterion. If the sulfur is retained, only the coal tested in test 38 retains all of the sulfur. This indicates that it contained sufficient silicon. The coal burned in Tests 32 and 33 contained sand. was not added. Although the available data is limited and disparate, The data indicate that the trapped sulfur was incompletely retained. Exam 34.35.3 In No. 8, sand was added to the burnt coal, but the improvement was from 81% to better than 100%. The molar ratio of Si/Ca was defined. Retention in these studies ranges from 71% to as high as However, the range was up to 95%.

The conclusion here is that by adding sand, the approximate Si/Ca molar ratio The retention of trapped sulfur was significantly improved depending on the ratio.

In general, with a few exceptions, a 2:1 calcium/sulfur molar ratio and a 1=1 silicon The element/calcium molar ratio can be used to determine the upper limit for sulfur capture and the release of Sol to the atmosphere. It is possible to fairly accurately predict the extent to which the output can be suppressed. Test 33.34. In 35, the predicted maximum sulfur capture was 6% higher than what was actually achieved. In all cases, the predicted acquisition was higher than the measured one. Ta. Based on a 1:1 silicon/calcium molar ratio, the predicted trapped sulfur retention is: It is reasonably accurate on average, with a margin of error of less than 2%. Instead, these The results indicate the proportion of bond-retaining material required for ideal suppression of SO2 emissions. general The data for this example shows that the calcium/sulfur molar ratio is approximately 2.0 and the silicon/calcium molar ratio is approximately 2.0. A sium ratio of approximately 1.0 provides ideal capture and retention of coal sulfur. Make sure that.

Fruit 1” LE Spring Creek's low sulfur powder is burned in a low NOx/SOx burner. Estern Sbituminous coal has a relatively high concentration of 7 in the as-burned coal ash. ．． Contains 75% sodium.

After this coal test, the samples are mixed with burner slag and baghouse flyash. Collected from. These samples are 3°12 and 6.39% respectively. Contained sodium.

In the 3.12% slag analysis using whole ash as a tracer, coal At least 40 percent of the input sodium ends up in the slag pit. held in solid form. This indicates that 60 percent has volatilized.

The volatilized sodium is recondensed in the cooler area downstream of the burner (simulated) boiler. It condenses and recondenses, especially on the fly ash tips of the baghouse. However, 6.3 Analysis of 9 percent fly ash shows 82 percent of the input sodium concentration. However, it does not imply concentration of sodium by recondensation. Is this the exam? Other data from et al. were not sufficient to accurately balance sodium.

The available data indicates that between 40 and 82 percent of the sodium in coal is in solid form. It shows that it was held. Before entering the cooler area of the slag pit, Considering that the fuel gas is exposed to combustion gas temperatures of up to 1600° for many minutes. Even 40 percent retention is a significant amount. This data is extremely limited. Therefore, all of the sodium that is added to this burner along with the coal is This leaves a wide range of uncertainties, most of which are retained solidly in this burner. It is clear that it can be done.

Figure 1 Calcium/sulfur molar ratio international search report international search report LIS 8803931

Claims (1)

[Claims] 1(a) A mixture of sulfur-containing fuel, sulfur binder, and sulfur retention material is placed in the first combustion zone. to introduce and (b) The sulfur binding material captures and captures substantially all of the sulfur in solid form. By combining sulfur with nuclear sulfur retention materials, multi-fuel gas, solid sulfur-containing fly ash and under conditions of temperature and multi-fuel stoichiometry that produce combustion products including slag. combusting a mixture in the first zone; (c) Thermodynamically unfavorable conditions are normally required for sulfur capture by the binder. inducing an interaction between the sulfur, the binder, and the retaining material that holds the sulfur in a solid state. within the fuel-rich combustion zone at least at a temperature above the melting temperature of the solid mass so as to to burn the combustion products with The process of burning sulfur-containing fuels consisting of 2. The product according to claim 1, wherein the sulfur binder is a calcium compound. Seth. 3. The total molar ratio of calcium to sulfur in the mixture is at least 1.51. Process according to claim 2. 4. The total molar ratio of calcium to sulfur ranges from 1.5:1 to 2.5:1. Process according to claim 2. 5. The sulfur binder consists of one or more basic components, and is one of the basic components in the mixture. 2. The process of claim 1, wherein the molar ratio of sulfur to sulfur is 2:1. 6 The sulfur retaining material is made of a silicon compound or a mixture of a silicon compound and an aluminum compound. A process according to claim 1, which is selected. 7. The molar ratio of silicon to calcium contained in sulfur capture ranges from 0.6 to 1.2. 7. A process according to claim 6. 8. The molar ratio of silicon to calcium contained in sulfur trapping is in the range of 0.8 to 1.0. 7. A process according to claim 6. 9. Sodium is in the mixture, and the sodium is solidified in the first and second zones. 2. A process as claimed in claim 1, in which the material is captured and retained in physical form. 10. Claim 1, wherein at least a portion of the sulfur binder is in the coal. The process described in. 11 At least a part of the holding material is in the coal as set forth in claim 1. process. 12 The basic components are magnesium and calcium as set forth in claim 5. process.